Control system for pipe lines



2 Sheds-Sheet 1 H. THOMAS Filed sept. 1, 19:54

CONTROL SYSTEM FOR PIPE LINES 6% 3 9 Y l om, 2 v. .m J

July 28, 1936. THOMAS 2,049,233

CONTROL SYSTEM FOR PIPE LINES Filed Sept. 1, 1934 2 Sheets-Sheet 2mesa/@E l PUPPE/ ca/L47 1 n 44 42 Mae f2 A PRESSURE Umea/ have 4l*EIL/7415526 43 Sagra/:Afef J.

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Y HOFZHJ /J' 1W Pffff Arran/vf? jl;L Patented July 2s, 193s UNITED4STATES CONTROL SYSTEM FOR PIPE LINES Henry Thomas, Ridley Park, Pa.,assignor to Sun Oil Company, Philadelphia, Pa., a corporation of NewJersey Application September 1, 1934, Serial No. '142,516 a claims.'(ci. 13u-7s) The present invention relates to a control system for'pipe-lines or similar fluid pressure or hydraulic-,systems but morespecifically to automatic control systems for pipe-line booster sta- 5tions.

In the operation of pipe-lines, particularly designed for petroleumproducts, it is common practice to have surge tanks at the pumpingstations, or stations are placed in such location in the line that acertain natural reserve capacity is maintained in the line ahead of thestation. Where surge or storage tanks are used at the stations, suchtanks are, in eect, iloating on the incoming line to the station. Such atank allows a ow from the preceding station to come in at any rate,while the station in question also can take the oil at any rate, whetherit is at the same rate, or at a higher or lower rate than is beingsupplied by the preceding station. Since the level in the tank serves tomaintain apositive pressure on the -suction on the pump, there is nodanger of l the pump running dry or of failing to get its proper supplyof oil.

- station (meaning tank and station as a unit) must be equal, but it canvary up or down over a considerable period of time due to the reservecapacity in the tank. In such stations, the princithe oil level in thetank is kept within certain safe limits, but the pumps could becontrolled with the minimum amount of attendance.

- In the caseof booster pump stations where surge tanks are not used,however, the problem is to so control the operation of the pump or pumpsthat it will handle any amount of oil which is delivered to it and stillkeep the pump pressures within 4the safe and proper limits. Such astation has to take the flow from the preceding station at what- 40 everpressure may exist and raise this pressure to a pre-determined higherpressure. It is usually desired to keep the suction pressure at theinlet of a pump to a relatively low value and to limit the dischargepressure at the station to the maximum safe working pressure on theline. It is generally found desirable to be able to control stationoperation to` take care of ilow rates as low as one-half of the maximumcapacity of the line, occasionally almost to zero' capacity and again upto the maximum capacity. This change in-rate may occur over a relativelylong period of time. l

Centrifugal pumps, because of their characteristics, are especially wellsuited for the application o! control devices. They are generally op-Where such tanks are used,- the averagequantity of oil into and out of aerated by constant speed motors, although they may be driven by enginesor turbines. The centrifugal pumpmay also be driven at variable speedsby electric motor, engine or turbine.

In the operation of a pipe-line, especially one 5 used for handlinggasoline or other finished products, the rate through the line may varyto quite an extent, and, since the friction pressure drop of the liquidthrough the line is a function of the velocity or the rate of ow throughthe line, it 10 is quite obvious that the conditions at the boosterpump` stations will vary as the rate of ow varies. Hence, it will benecessary to make changes in the adjustments of the valves to and fromthev `pump (or in the speed of the pump in the case 15 of variable speeddrive). To illustrate this condition, let us assume that there are vepumping stations operating on a length of line. These stations arelocated 50 miles apart and all at approximately the same elevation.Between some 20 of these stations there may be an outlet line whichtakes delivery from the pipe-line. The ilrst station of the ve takes itssupply from a storage tank, the other four stations serve as boosters toraise the pressure in the line to give 25 the required ow. With a givensize line, and with a rate of 500 barrels per hour. each station y willdeliver the oil at a pressure of 800 pounds and pal duties of theoperators would be to see that deliver it to the following station at apressure of 50 pounds. Assuming that at this rate through- 30 out thelength of the line the inlet valve to the pump and the outlet valve tothe pump are wide open and the system will continue to maintain the sameconditions with practically no change.

If,/however, itis necessary, due to any con- 35 dition at the deliveryend or at the receiving end of the line, or any intermediate point inthe line, to change the rate of ow through the line, it (will benecessary to make changes in the valve settings at all or a part of thestations along the 40 line. For example, if there is a side outlet fromthe line between #3 and #4 stations which may take barrels per hour,then the settings of the valves at #1, #2 and #3 stations will remainpractically the same as the original settings, 45 while it willbenecessary to readjust the valves on Stations #4 and #5, since there isnow only 400 barrels per hour flowing through this part oi.' the lineand this change has brought about a difference in pressure drop and thiscan be 50 taken care of only byvarying the valve position (or by varyingthe speed of the pump) to give the same results.

Another example of changes which might occur is the case where the #5station may not be 55 5; I I Y 2,049,233

since the now has been reduced from 500 barrelsper hour to 300 barrelsper hour, and, as a re-l suit, the friction drop is reduced to aboutone- .15 half of the previous friction drop and an excess pressure ofbetween 300 and 400 pounds would build up between each station. Withouta change in the adjustment of the stations, however, this would notappear as an excess of 300 to 400 pounds on each station butthe pressurewould be accumulated so that Station #5 would build up an excesspressure of 1500 to 1800 pounds, and the last stations on the line wouldhave exceedingly high suction pressure, which would make it verydangerous to operate a pump.

With the proper control at each station this excess pressure would betaken care of by throttling through the valves. 1

, The above examples simply illustrate some of 80 the conditions whichmay bring about changes requiring the readjustment of the stationconditions. Many other changes which take place in the pipe-line systemrequire readjustment oi the station conditions, in some cases to prevent$5 excessive pressures, :in other cases to prevent damage to pumps dueto lack of proper supply of the oil or liquid being handled.

There are many devices which have been used which would automaticallyshut down the pump 40 in the case oi.' pressures becoming too high ortoo low or to take care of other abnormal conditions. Itis not theurpose, however, of this control I to simply shu| ,down the stationsunder these conditions, ,since shutting down a station does notalways'remove the dangerous condition. It

is,however', the purpose to control the operation of each station tokeep it within the safe operating limits .under any operating conditionswhich may be brought about throughout the entire line. This controlunder certain conditions may even shut down certain pumps or stations.

Such a shutdown might be governed by pressure; excess flow, or otherabnormal conditions.

l It is obvious from the foregoing that in the operation of a linecarrying a liquid which, due

to its incompressible nature, gives practically no elasticity to theoperation of the system, that a change in one part of the system adectsmany or all of the other stations. Any form of manual control not onlydemands constant and undivided attention on the part of the operator butit would also result in uneven operation and ilow of the pipe-line andin many cases might result in dangerous conditions. I have discoveredthat certain control instru-- ments well known in the art may be used tocontrol a booster station in such a manner as to prevent damage to thepump and to maintain the ow in the pipe-line at such a rate as to meetlthe conditions at the other stations and ofthe line.

It is therefore an object of the present invention to provide a controlsystem which is automatic and positive in operation, requiring a lminimum of care and supervision and one, which if it should fail, 'willnot result in ge to the pumping equipment or pipe-line generally. Theseand other objects will appear as the de= scription progresses. i

For an understanding of the invention, reieri' ence is made to thespecification hereiubelow and to the drawings accompanying the saine andforming a part thereof in which:

\ Fig. 1 is a diagrammatic representation ofthe system; and 1o Fig. 2 isa diagrammatic representation of the control instrument, two of whichare employed.

Referring now to the drawings: I i represents a pipe-line through whichuid is being transmitted in the direction indicated 5 by the arrows. Abooster pump I2, which may be of any suitable type such as a multistagecentrifugal pump oi the type customarily used in booster stations, isoperatively connected to and driven by a suitable prime mover hereindicated 20 as an .electric motor I3, connected by leads 2| throughswitch 26 to a source of electrical energy as a power line 28. The pumpI2 is connected to the pipe-line II by means of an inlet pipe Il and anoutlet pipe I5. Located in the pipe-line 25 Il between inlet pipe I4 andoutlet pipe I 5 is a check valve I6 whichpermits-the Vfluid to ilow`directly through the pipe-line as soon as the station pump is cut off.There is also a check-valve Il placed in the outlet pipe l5 whichprevents 30 backflow into the station. Two manually operated valves I8and I9 are placed in the inlet pipe I4' and outlet pipe I5 respectively,for manually controlling the ilow if desired or for closing the lines tothe station when not operating. l

The pump I2 isidesigned to receive the fluid y being transmitted throughthe pipe-line II at a fairly constant pressure, generally between 25 topounds and to increase the pressure oi the nuid to the desired outletpressure generally 40 about 800 or 900 pounds.

In order that the inlet pressure to the pump maybe maintained constantat the desired pressure, the balanced diaphragm valves l and l areplaced in the outlet and inlet pipes I5 and 45 Il respectively. Thevalve I is operated by air ,which is fed and vented through line 2. The

` air for operating this valve or the venting of line 2 to relieve thepressure therein, is controlled by controller3 which is operated by a 50i capillary pressure line I extending from the inlet I4 betweenthe valve5 land the pump l2. The valve 5 is operated in a similar manner by airwhich is fed and vented through line G; 'I'he air for operating thisvalve or the venting of 'line 55 6 to relieve the pressure therein, iscontrolled by controller 1, substantially identicalwith controller 3,and operated by a capillarypressureline 8 vextending from the inlet I4between the pump I2 and the valve 5. Air under pressure for cpno eratingthe valves I and 5 is fed to the controllers 3 and 1 by means of the airfeed line 26 from a suitable air supply source 2i. 'Ihe particular typeof balanced diaphragm valves I and 5 form no part of the presentinvention and any c5 suitable valves may be used.

The controllers 3 and 'l may be of any desired type and construction anddo not form part of the present invention, however for the sake ofclarity there is illustrated in Fig. 2 the operat- 70 ing mechanism ofone form o! controller.

.Referring now to Fig. 2:

The numeral Id designates (as in Fig. l) the 'inlet to pump I2. The lineI6 contains manuthecontroller 1, and capillary lines 4 and 8 leading tocontrollers 3 and 1 respectively. As hereinbefore pointed out, air foroperating valves I gauge 3I, and passes through conduit 32 and port 33in adjustable valve seat 34. Thence, as-

suming valve 36 to be raised from seat 35, it

passes through conduit 38 and line 6 to the diaphragm motor controllingvalve 5, thereby openi ing 'valve 5, theair pressure in conduit 88, line6 and the diaphragm motor being indicated by pressure gauge 39.Simultaneously air is passing throughvv line 40 from conduit 32 topressure reducing valve 4I and thence through line 42 to branched line43. One branch'line 43 leads to nozzle 44, the orifice of which iscontrolled by flapper valve 45 which is operated by the pipelinepressure operating through capillary tube 8, helix 41 and -link 45. Theother. branch oi' line 43 passes to a diaphragm 48 which operates valve36 by means of 'valve stem 49.

Assuming now that the' pressure in line I4 leading toI pump I2 is thedesired pressure and'correct and constant. In this case valve 36 will beseated on seat 31 thereby permitting the air pressure to maintain thecontrolled valve in line I4 in a full open position. The pressure inline I4 will be transmitted through capillary tube 8- to helix 41 but,under the conditions above prescribed, will be insuilicient to operateiiapper valve 45 to close nozzle 44. Air passing through conduits 42 and43 will thus be vented throughl nozzle 44. 'Assuming now that thepressure in line I4, between valve 5 and pump I2, rises above thedesired limit. 'Ihe pressure will then be sufficient to operate valve 45to partly throttle openlng in nozzle 44, permitting pressure to build upin line 43 and diaphragm 46. Diaphragm 48 then partly unseats valve 36from seat 31, venting"a portion of the air from lines 38 and 6 andpermits the spring opposing the diaphragm in valve 5 to partly closevalve 5 until the pressure in line I4 falls to itsproper upper limit.Any'sudden and great rise in pressure would, of

course, completely close apper valve 45 and nozzle 44 and thus closevalve 5.

In order to prevent or minimize "hunting or over control" in the system,a control valve' compensator is provided in the line 6 through which airis fed and ventedv from diaphragm valve 5. This control valvecompensator consists of a differential pressure motor 50 connected toline 6, this motor is also connectedv through bell crank 5I and link 52to air nozzle 44 which is mounted ony a common axis with flapper valve45. When the air is vented from line 6, due to anincrease in pressure inpipe I4, as described above, the differential pressure motor,.throughbell crank 5I and link 52, will move air nozzle 44 about its axis awayfrom fiapper valve 45, thus preventing any over-control and causing thediaphragm valve 5 to close gradually. When the pressure in pipe I4decreases the control valve compensator causes diaphragm valve 5 to opengradually and prevents the apper valve from causing too great an openingof the diaphragm valve, and thus causing an over-travel and a' huntingaction in the system.

Controller 3 operates in substantially the same manner as controller 1,its parts being identical except that in controller 3 the helix isreversed as compared with -helix 41 in controller 1. Briefly statedthen, when the pressure in line I4 at the junction of capillary line 4therewith is correct and constant, the valve 36 will be seated on seat31and pipe-line valve I will be held in '5 its wide open position by thepressure of air 'ad-V mitted to the diaphragm in the valve through line2. Ii the pressure in line I4.falls below a' prescribed minimum, thehelix in controller 3 close it at pressures above, say 504 pounds andthe helix -in the controller 3 being set so as to operate its ilapper toclose at a pressure below say 40 pounds. Thus on failure of the airsuplply in line 2l the air in diaphragm controlled valves I and 5 andlines 2 and 6 would be vented 25 either past valve seat 31 to theatmosphere or past valve seat through lines 32 and 40, re#` ducing valve4I, line 43 and nozzle 44 to the atmosphere, all depending on thepressure in lines 4 and 8. By this arrangement both of valves I and 5would close, passing the pipe-line ilow through check valve I6. Otherdevices described hereinafter would shut th'e motor and pump down. y

In case of power failure the pressure in line I4 adjacent the junctionof lines 4 and 8 would rise, l thereby operating valve 6 to close it.Such ac tion would cause the iluid in pipe-line II to flow through checkI6 but its iiow into outlet line I5 would be prohibited by check valveI1.

The operation of the control means is as iollows:

Assume the pump I2 to be designed to operate with an inlet pressurewithin the range -60 pounds and the controllers 3 and 1 adjusted tomaintain the inlet pressure within the desired range. Consider that thepressure in the inlet pipe I4 is within the desired range, the valves Iand 5 are then wide open and the pump I2 is operating to boost the linepressure to 900 pounds.

If the inlet pressure' drops, due to the station preceding it slowingdown or an outletfin the line being opened, to below 40 pounds, thisdrop causes thel capillary pressure line 4 to operate .the controller 3venting air from line 2 and thus operating valve I to throttle it,thereby cutting down the throughput through the pump I2 and raising theinlet pressure until it reaches its normal pressure range. Suppose nowthat the feed to the station has increased and has thereby 60 jraisedthe inlet pressure abovef pounds. As

the inlet pressure increases the pressure in the capillary tube 8operates controller 1 to vent air from the tube 6 and throttle valve 5,thus cutting down the pressure to the inlet of the pump until it reachesits normal range. The pump would normally operate with a variation insuction pressure of l5 to 20 pounds per square inch; therefore theoperating pressures for actuating controllers 3 and 1 should be spaced70 apart by this` amount. By so doing, it is to be noted that controlvalves I and 5 will not function at the same time. 'I'hat is, if theinlet pressure falls, valve I may be completely closed, but valve 5will`remain wide open. If the inlet pres- 75 rtially closed the valve ie begins to increase when valve i is wholly or be opened sumciently tomaintain the inlet pressure at approm'- mately 50 pounds persquare inchuntil valve i is completely open. if the inlet pressure con= tinues to`increase valye d will then be operated to partially reduce it, andvalve 5 may be closed or almost completely closed but valve i willremain wide open.

On the inlet line it a suitable low pressure trip is is installed, thuswhen any predetened low pressure is reached, which is always much lowerthan the normal operating pressure, this trip will operate to close thecircuit from a battery 2d Y v. a the solenoid 25 and open switch it thuscutting od the motor is.

e it is preferred to have the controllers and l ,vent air from the lines2 and d respectively in order to throttle valves i and t so that in caseof iailure of the air supply the system will-be equivalent or evendierent apparatus, whether electrical or iluid pressure, may be usedfior efiecting the desired control of the inlet pressure withoutdeparting from the spirit or scope of this invention.

It is also to be noted that while the present invention has beendescribed as specically ap plied to oil transportation pipe-lines. it isjust as applicable to all lines under pressure induced by pumps.lTherefore when pipe-line is used specilcally in the claims, it is meantto include any uid carrying line having a pump associated therewith forboosting the pressure in such line. at I claim, and desire to protect byLetters Patent is as follows:

l. In a pipe-line system, the combination of a pipe-line. a pump in saidpipe-line, a bypass around said pump, a controlled valve in the inletside or said p a controlled valve on the outlet side of said pump, meansomrable by an in crease in pressure above a predetenr. maximum on theinlet side oi said pump to throttlev said controlled valve on the inletside of said pump, and means operable by a decrease in pressure below apredeteedminimum on the intake side of said pump to throttle saidcontrolled valve on the outlet side o i said p.

2. An automatic control system for pipe-lines comprising in cbination, apipe-line, a pump in 10 y said pipe-line, a by-pass around said pump,'avalve onA the inlet side of said pump, meansresponsive to an increase inpressure on the inlet side of said pump to throttle said. valve, a valveonthe outlet side of said pump, and means re- 15 sponsive to a decreasein pressure on the inlet side of said pump to throttle said valve on theoutlet side of said pump.

3. ln a pipe-line system, the combination of a lpipe-line, a pump insaid pipe-line, a bypass 20 aroundsaid pump, a diaphragm operated valvein said pipe-line on the inlet side of said pump, means for conductingoperating` fluid to said valve, means for controlling the admission' ofoperating fluid to said valve, means responsive 25.'

to an increase in pressure in said pipe-line on the inlet side of saidpump to actuate said con trol means to admit operating duid to saiddiaphragm valve to throttle it, a diaphragm operated Vvalve in saidpipe-line'on the outlet side of said 30 pump, means for conductingoperating uid to' said second valve, means for controlling the admissionof operating iluidto said second valve, means responsive to a decreasein pressure in said pipe-line on the inlet side of said pump to actuatesaid control means 4to Vadmit operating duid to said second diaphragmvalve to throttle it.

d. ln-a pipe-line system, the combination of a pipe-line, a pump in saidpipe-linea by-pass V Mound Said Pump; a valve in said pipe-line on theintake side of saidpump, control means for the throttling of said valve,means responsive to an increase in pressure in said intake side toactuate said control means, a valve in said pipe-line on the outlet sideof said pump, control means for the throttlingl of last named valve,means responsive to a pressure decrease in said intake side to actuatethe last named control means.

